1. Field of the Invention
The present invention relates to an apparatus for detecting tire air pressure for a motor vehicle, which is operable to lower the speed of the vehicle when the tire air pressure becomes lower than a predetermined value and reliably indicate to a driver of the vehicle that a reduction in tire air pressure has occurred.
2. Description of Background Art
One apparatus for detecting whether the air pressure of a tire for a motor vehicle has been reduced or not is known from Japanese Patent Laid-open No. Hei 9-240446 entitled xe2x80x9cBRAKE CONTROL APPARATUSxe2x80x9d, for example.
FIG. 4 of the above publication shows a brake control apparatus, wherein when the air pressure of the tire of a left or right front wheel becomes lower than a predetermined value, and the rate of reduction of the air pressure is equal to or higher than a predetermined value based on signals from a left front wheel air pressure sensor 14 and a right front wheel air pressure sensor 15, a solenoid-operated valve associated with the wheel laterally opposite to the wheel whose tire air pressure has been reduced, i.e., a left front wheel solenoid-operated valve 49 or a right front wheel solenoid-operated valve 50, is operated to brake the right front wheel or the left front wheel, and a warning unit 8 is actuated.
With the apparatus disclosed in the above publication, however, the wheel is braked only under the condition when the air pressure of the tire is lowered. Accordingly, if the wheel is braked while the throttle opening is increasing, the wheel may not be braked sufficiently and hence the vehicle speed may not be lowered, since the engine output is increasing.
Furthermore, since solenoid-operated valves for braking the wheels are required for the respective wheels, the apparatus has a high cost and a complex process to control those solenoid-operated valves is required.
In addition, it may be difficult for the driver of the vehicle to confirm the warning from the warning unit 8, if the vehicle is being operated in bright and/or noisy areas.
It is an object of the present invention to provide an apparatus for detecting a tire air pressure for a motor vehicle, which is capable of {circle around (1)} lowering the speed of the vehicle easily with a simple arrangement and {circle around (2)} reliably indicating a reduction in the air pressure to a driver of the vehicle when the tire air pressure becomes lower than a predetermined value.
To achieve the above object, there is provided, in accordance with a first aspect of the present invention, an apparatus for detecting tire air pressure for a motor vehicle includes tire air pressure detecting means for detecting the air pressure of the tire of the motor vehicle, and control means for comparing an actual air pressure detected by the tire air pressure detecting means with a stored air pressure threshold. Furthermore, the engine output is controlled when the actual air pressure becomes lower than the air pressure threshold.
In order to control engine output, several processes are available which include {circle around (1)} adjusting the throttle opening of the engine, {circle around (2)} performing ignition control so as not to increase engine rotational speed beyond a predetermined value, {circle around (3)} cutting off the fuel, and {circle around (4)} changing the resistance of an AC generator. These processes are carried out by control means to control the engine output to lower the vehicle speed.
In accordance with a second aspect of the present invention, an apparatus for detecting tire air pressure for a motorcycle includes tire air pressure detecting means for detecting the air pressure of a tire of a motorcycle, wherein the actual air pressure detected by the tire air pressure detecting means is compared with a stored air pressure threshold. If the actual air pressure becomes lower than the air pressure threshold, a light-emitting member or a sound-generating member disposed on or around an instrumental panel of the vehicle is operated to issue a warning.
When the actual air pressure of the tire drops below the air pressure threshold, the light-emitting member or the sound-generating member disposed on or around the instrumental panel is operated to issue a warning. Even in bright and/or noisy areas, the light-emitting member is easily visually recognizable in the same manner as other various instruments in the instrument panel. This allows a motorcycle driver to be reliably informed of the reduction in air pressure. It should also be noted that it is more preferable to operate both the light-emitting member and the sound-generating member in order to ensure that the driver is informed of the reduction in air pressure under various driving conditions.
According to a third aspect of the present invention, an apparatus for detecting a tire air pressure for a motorcycle includes tire air pressure detecting means for detecting the air pressure of a tire of a motorcycle, wherein the actual air pressure detected by the tire air pressure detecting means is compared with a stored air pressure threshold. When the actual air pressure becomes lower than the air pressure threshold, a light-emitting member or a sound-generating member installed in a driver""s helmet is operated to issue a warning.
When the actual air pressure of the tire drops below the air pressure threshold, the light-emitting member or the sound-generating member disposed in the driver""s helmet is operated to issue a warning. Accordingly, even in bright and/or noisy areas, the light-emitting member is easily visually recognizable, allowing a motorcycle driver to be informed of the reduction in the air pressure. It should also be noted that it is more preferable to operate both the light-emitting member and the sound-generating member in order to ensure that the driver is informed of the reduction in air pressure under various driving conditions.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.